Various machines are provided with sliding members that relatively move while being slidably in contact with each other. In a system having such sliding members (referred to as a “sliding system” in the present description, e.g. a sliding machine), the friction coefficient between the sliding surfaces may be reduced thereby to reduce the sliding resistance and it is possible to enhance the performance and reduce the operational energy. Moreover, the reduced friction can also contribute to improvement in the durability, reliability and other necessary properties of the sliding system.
Sliding properties (in particular, the friction coefficient) are different depending on the surface condition of each sliding surface during the operation and the lubrication state between the sliding surfaces. In order to enhance the sliding properties, various studies have heretofore been made to modify the sliding surfaces and improve the lubricant (lubricant oil) which is supplied between the sliding surfaces. Descriptions relevant to the above studies are found, for example, in Patent Literature below.